FreeBird (oz13151)

About this Plan

FreeBird. Radio control sport aerobatic model, for .40 two stroke engines.

Direct submission to Outerzone.

Update 07/07/2021: Added article, thanks to RFJ.

Quote: "Freebird was designed during a period of convalesence after a fairly major operation. My normal approach of hack away with a balsa knife and design it as you go along was not possible. The handywork of someone else with a sharp knife had seen to that. This was probably quite a good thing as it gave me much more time to think about what I wanted from this new design.

Midmounted plug-in wings and a glider-style all-moving tail appealed for a change. With these features I decided to build in some shape to the fuselage, without having to invest in half a rainforest to achieve it.

Thus Freebird was conceived. Powered by a 0.40 two stroke, it's racey lines, spirited flight performance complement well with what has turned out to be a thoroughly practical and pleasing model to fly.

Fuselage construction: The shape of the fuselage is mainly created by bending 1/8in balsa sheet around the main formers and not by using huge section balsa block, most of which ends up on the work shop floor.

The accuracy of the fuselage starts, most importantly, with the assembly F2, F3 and doublers Dl. Before the assembly is glued, I used cyno for this, sandwich the two Dl's together and pre-drill the five holes. This saves a lot of aggravation later on.

Cut the fuselage sides from well matched 1/8in balsa medium sheeting, choosing pieces that will bend easily across the grain.

The fuselage sides are firmly glued to D1. When dry they can be coerced around F2 and F3, some cyno and accelerator makes this job very easy. Please note the actual shape of the fuselage side sheet is larger than the side elevation on the plan. This is because it has to bend around Fl, F2, F3 and a little bit of F4. The dotted line on the plan shows approximately the extra material required.

Next add F1, again bend the fuselage side around the curved section. Sand the lower sheet to form a flat on the bottom of formers Fl, F2, F3 and F4, then add the 1/4in balsa bottom sheet and carve to a pleasing round shape similar to one shown on the plan. Now laminate Fl with good quality 1/16in ply, shown as HA on the plan.

The fuselage doublers, D2 and D3 are added next. I found that contact adhesive coped best with the curved part on the lower part of F3.

Follow this by adding formers F4-F6. The balsa immediately behind F3 won't like this too much so a little heat or steam may be necessary.

Add the 3/16sq longeron and sheet the upper turtle deck with 3/32in sheet. This is probably the hardest part as care is needed, especially around F6.

By now you should have the beginnings of a lightweight, pleasingly shaped fuselage, hopefully inspiring you to push on with the model.

At this stage it's better not to add the bottom sheeting, or the block between F1-F2 as access for control runs is needed. Fuel tank and engine installation is also made much easier.

Fin and tailplane: The fin is made from a core of 1/4 in balsa covered with 1/16 balsa either side. Note the 1/4 in core is two pieces of balsa, the grain direction is the same as the 1/16 sheet except for the stern post.

The all-moving tail is moved by a snake embedded in the 1/4 in balsa core. The best way to achieve this is to start with a 1/16 side, add the 1/4 in core, epoxy in the snake outer and finish the assembly with the second 1/16 sheet. Finally inlay some 1/16 ply sheet around the pivot point and sand the complete assembly to that shown on the plan. The rudder is made from 3/8in sheet, again sand to section on plan..."

Supplementary file notes

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